Method for producing adhesive closing parts

ABSTRACT

The invention relates to a method for producing adhesive closing parts, whereby adhesive closing elements are formed from a plastic material. In order to produce at least one adhesive closing element ( 3 ) without a form tool in at least one partial area, the plastic material is deposited in the form of drops which are successively delivered by means of at least one application device ( 9 ), and the locations of the deposition of the drops are selected in a three-dimensional manner in view of the form of the respective adhesive closing elements ( 3 ) to be produced.

[0001] The invention relates to a process for producing adhesive closing parts in which individual adhesive fastener elements are made from a plastic material.

[0002] A process of this type has already been proposed in DE 198 28 856 C 1. Application of this process is found to be relatively costly when adhesive fastening parts are to be manufactured in which the adhesive fastener elements are very tightly packed and small. This is the case, for example, in manufacture of so-called microfasteners in which the adhesive fastener elements are provided in the form of stems thickened at the end or with side projections in very high packing densities of 200 or more adhesive fastener elements per square centimeter, for example. Shaping tools such as dandy rollers are required to shape the stems at the end. High production costs are incurred because of the very large number of openings in the roller, which may be produced by etching, electrodeposition, or laser machining.

[0003] On the basis of this state of the art the invention has the object of developing a process permitting very cost-effective production of adhesive fastener elements in the widest possibly variety of desired shapes.

[0004] In a process such as that referred to above it is claimed for the invention that this object is attained in that at least one adhesive fastener element in at least one partial area is formed without use of a shaping tool in that the plastic material is deposited in consecutive drops by means of at least one application device and the locations of deposit of the drops selected are three-dimensional relative to the respective adhesive fastener element to be formed.

[0005] The buildup of the adhesive fastener elements claimed for the invention by the smallest possible individual drops which are deposited in succession at selected locations permits formation of the adhesive fastener elements in any configuration in drops virtually as small as desired and in the greatest packing density desired, without necessitating development of correspondingly costly shaping tools. Thus, control of the locations of deposit of the drops, accomplished by means of corresponding relative movements between application device and a substrate carrying the deposit, preferably under computer control, permits production without great difficulty not only of the shapes of adhesive fastener elements indicated in DE 198 28 856 C1, such as stems with mushroom heads, but also of shapes which can be produced only with great difficulty or not at all by use of conventional shaping tools, such as loops, hooks, or anchors, that is, shapes which could be produced only poorly, or not at all, with a shaping tool because of the undercuts present.

[0006] It is claimed that the process claimed for the invention may be employed for production of adhesive fastener elements in which various types of materials may be used as a backing element from the surface of which the adhesive fastener elements project. In other words, a plastic material, especially one in sheet form, may be used as the substrate on which the drops forming the adhesive fastener elements provided for the respective application purposes are deposited.

[0007] When a plastic material is used as backing element, the process carried out may be one in which the drops forming the adhesive fastener elements are deposited on the finished backing element. However, it is also possible to form both the adhesive fastener elements and the backing element from drops deposited. For example, a sheet of plastic making up the backing element and the adhesive fastener elements present on the sheet may be built up in a single production pass from droplets sprayed on by means of application devices.

[0008] Textile materials, such as ones in knitted or woven form, may be used as the material of the backing element in place of plastic. The backing element need not be a flat body. Shaped bodies on whose surface the projecting adhesive fastener elements are formed by means of the pertinent application device may be provided for special applications.

[0009] Use is made preferably of an application device having at least one nozzle from which the plastic material is sprayed in droplets of a size of a few picoliters. Nozzle devices such as this may be actuated by piezoelectric or electrothermal means to centrifuge the liquid plastic material. The plastic material preferably consists of acrylate which sets after deposit of each drop or group of drops, for example, after the location of deposit has been subjected to ultraviolet radiation. The plastic may, however, also be a thermoplastic which is caused to set by chemical means or in another manner.

[0010] Construction of the adhesive fastener elements may be carried out at high operating speed, since the droplets may be sprayed in succession at a high rate. Rates of several kilohertz may be reached immediately in computer-controlled operation. An application device may also be provided with a plurality of nozzles operated simultaneously in order to construct a plurality of rows of adhesive fastener elements simultaneously.

[0011] The invention is described in detail in what follows on the basis of exemplary embodiments illustrated in the drawing, in which

[0012]FIG. 1 presents a highly simplified diagrammatic perspective view of one exemplary embodiment of a device for application of the process claimed for the invention;

[0013]FIG. 2 a diagrammatic side view of the device shown in FIG. 1;

[0014]FIG. 3 an enlarged presentation of the area designated as A in FIG. 2;

[0015]FIG. 4 a side view of the device similar to that in FIG. 2, the production of adhesive fastener elements in the form of loops being shown;

[0016]FIG. 5 an enlarged presentation of the area in FIG. 4 designated as A;

[0017]FIG. 6 a highly simplified diagrammatic side view of a device for production of adhesive fastener elements with trough-shaped heads by calendering; and

[0018]FIG. 7 an enlarged presentation of the area in FIG. 6 designated as A.

[0019] FIGS. 1 to 3 serve to illustrate the process claimed for the invention on the basis of an example in which the adhesive fastener elements with a backing element 1 in the form of sheet polyethylene on one surface of which adhesive fastener elements 3 are formed as stems thickened on the ends. In the example shown in FIGS. 1 to 3 the thickened ends are in the form of mushrooms, as is to be seen in FIG. 3 in particular. For the sake of clarity the adhesive fastener elements in all the figures are shown in greatly exaggerated size and spaced at greatly exaggerated distances from each other.

[0020] The backing element 1 is mounted on a guide roller 5, which may be driven in both directions of rotation for execution of controlled rotational steps, so that the backing element 1 may be moved back and forth in the direction of a Y axis relative to the location of deposit of drops situated within an area of application A (see curved arrow in FIG. 2). Droplets of liquefied plastic are deposited by means of an application device 9, which itself is movable in the direction of the Z axis (see double arrow 11 in FIG. 2) and in the direction of the X axis perpendicular thereto (see double arrow 13 in FIG. 1). Consequently, the location selected for droplet deposit relative to the backing element 1 may be three-dimensional, as a result of corresponding movement of the guide roller 5, and accordingly of the backing element 1 and the application device 9. As an alternative, the application device 9 could be movable along all three axes (X, Y, and Z) relative to the backing element 1.

[0021] In the example illustrated in FIGS. 1 to 3 the application device 9 has a nozzle spraying the liquefied plastic. In the operating state shown in FIG. 3 the nozzle 15 assumes a position relative to the backing element 1 such that the stem of an adhesive fastener element 3 is built up by sequential spray application of droplets each of a volume of a few picoliters. In the state illustrated in FIG. 3 the stem sprayed on through the nozzle 15 is built up to approximately one-third its height. The droplets are sprayed, preferably under computer control, at a high frequency of 2 kilohertz, for example. The droplets deposited in each operation are hardened during the intervals between the spraying processes; this can be accomplished in different ways, for example, by spray application of a setting agent or by supply of energy, especially by ultraviolet radiation. In the present example, nine ultraviolet lamps 17 for irradiation of the application area A with ultraviolet radiation are mounted beside the application device 9. For the setting processes the application device 9 is returned preferably in the direction of the Z axis and/or the backing element 1 is displaced in the direction of the Y axis by movement of the guide roller 5, before the corresponding elements are brought back to the position corresponding to the location selected for droplet application.

[0022]FIGS. 4 and 5 serve to explain the execution of the process for adhesive fastener elements 19 in which adhesive fastener elements in the form of loops are formed on the backing element 1. The process applied is such that initially two stems 23 are built up for each loop and are then bent over in arcs as illustrated in FIG. 5.

[0023]FIGS. 6 and 7 illustrate the production of adhesive fastener component parts with adhesive fastener elements 21 which are formed by first building up stems 23 without thickened areas on the ends. A compression gap is formed by means of a calender roller 25, which operates in conjunction with a mating roll 27; thickened end areas of the adhesive fastener elements 21 are formed which are trough-shaped (see FIG. 7) by calendering on the ends of the stems 23.

[0024] Liquefied acrylates the viscosity of which may be adjusted by addition as desired of a reactive thinner, for example, are suitable as plastic material to be applied in droplet form. The hardenability by means of ultraviolet radiation can be enhanced preferably by addition of a photoinitiator.

[0025] In one example the plastic material contains as acrylic material 90 percent Ebecryl 4835, a prepolymer made by the UCB company, 8 percent HDDA (UCB company) as reactive thinner for viscosity adjustment, and 2 percent Darocur 1173, made by the Ciba-Geigy company, as photoinitiator.

[0026] In another example, 90-percent Ebecryl 4835 and 4-percent Ebecryl 230 from the UCB company are provided as acrylate materials. 4-percent HDDA from the UCB company is employed as reactive thinner and 2-percent Darocur from the Ciba-Geigy company as photoinitiator.

[0027] Plastic materials of a different composition may, of course, also be employed for application of the process claimed for the invention. Backing elements of a different nature, such as textile materials, or molded elements provided for special applications may be used in place of a sheet of polyethylene.

[0028] The invention has been described in the foregoing on the basis of examples in which the adhesive fastener elements as a whole are in the form of droplets spray-applied in succession. The process may, of course, also be applied to advantage in such a way that simply formed stems of adhesive fastener elements may, when straight stems, for example, are involved, be produced conventionally with shaping tools, with no additional expense, as initial material onto which droplets of the geometric configurations desired are then sprayed to produce finished adhesive fastener elements. 

1. A method for producing adhesive closing parts in which individual adhesive fastener elements (3; 19; 21) are formed from a plastic material, characterized in that at least one adhesive fastener element (3; 19; 21) in at least one component area is formed without use of a shaping tool in that the plastic material is deposited by means of at least one application device (9) in the form of consecutively released droplets and the locations of deposit of the droplets is three-dimensional relative to the shape of the adhesive fastener elements (3; 19; 21) to be formed at a time.
 2. The process as claimed in claim 1, wherein the droplets forming the adhesive fastener elements (3; 19; 21) are deposited on a backing element (1).
 3. The process as claimed in claim 2, wherein a plastic material is used as backing element (1).
 4. The process as claimed in claim 3, wherein the backing element (1) is also built up by deposit of droplets released by at least one application device (9), as are the adhesive fastener elements (3; 19; 21).
 5. The process as claimed in claim 4, wherein a backing element (1) in the form of a sheet is used.
 6. The process as claimed in claim 4, wherein a textile material, in particular in knitted or woven form, is used as backing element (1).
 7. The process as claimed in claim 4, wherein a molded element, in particular a profile element, is used as backing element.
 8. The process as claimed in one of claims 1 to 7, wherein the application device (9) has at least one nozzle (15) and wherein the plastic material is sprayed from the nozzle (15) of the application device (9) with a droplet volume of a few picoliters.
 9. The process as claimed in claim 8, wherein a liquid plastic is sprayed from the nozzle (15) as plastic material.
 10. The process as claimed in claim 8 or 9, wherein both the backing element (1) and the at least one nozzle (15) are moved for three-dimensional control of the locations of deposit of the droplets.
 11. The process as claimed in claim 1 to 10, wherein the plastic material is solidified after deposit of each droplet or group of droplets.
 12. The process as claimed in claim 11, wherein the solidification takes place as a result of delivery of energy.
 13. The process as claimed in claim 12, wherein the delivery of energy occurs as a result of electromagnetic radiation, in particular ultraviolet (UV) radiation or infrared (IR) radiation, or as a result of chemical reaction.
 14. The process as claimed in one of claims 11 to 13, wherein the backing element (1) and/or the application device (9) is or are moved for the purpose of solidification to a location which differs from the position assumed in preceding deposit of the droplet.
 15. The process as claimed in claims 11 to 14, wherein the plastic material has after solidification a flexibility, which may be predetermined, which is suitable for hooking or release of the adhesive fastener elements (3; 19; 21).
 16. The process as claimed in one of claims 1 to 15, wherein the droplets are deposited at a frequency of more than 50 hertz, preferably a frequency in the kilohertz range. 